The invention relates to an arrangement for the fine machining of rotationally symmetrical, disk-shaped or annular components by vibratory grinding, as described in the preamble to claim 1.
Current developments in the field of aircraft gas turbine engines show a clear tendency towards the use of integrally bladed rotors, particularly in the compressor region. In this respect, requirements for less weight, higher strength and less wear are decisive, thus permitting higher speeds/higher power and longer life. For the individual stages of such rotors, i.e. for integrally bladed rotor disks, the designation xe2x80x9cbliskxe2x80x9d derived from xe2x80x9cbladed diskxe2x80x9d, has become general in specialist circles. In the case of larger blisks, the blades are usually manufactured separately, for example by forging or casting, and are connected to the disk by means of appropriate welding methods, for example by means of linear friction welding, the disk frequently being a forged part. Smaller to medium sized blisks are usually manufactured from the xe2x80x9csolidxe2x80x9d, i.e. from a single blank. The disk contour can be largely generated by turning up to the point of the fine machining. The geometrically demanding blade region is preferably generated by multi-dimensional milling, although the fine surface finish and surface accuracy necessary for aerodynamic and strength reasons are not yet completely achieved (xe2x80x9cmilling linesxe2x80x9d). For this reason, final fine machining is necessary in this case. However, even in the case of relatively large, welded blisks or other components, such as disks, guide vane rings, etc., final fine machining can be necessary or advantageous.
A promising process for this purpose is liquid-supported vibratory grinding which, in a preferred version, presents a combination of mechanical abrasion and chemical erosion (currentless, i.e. without external electricity sources). In this process, a relative motion between a multitude of loose abrasive particles and the workpiece is generated by mechanical vibrations of a container, wetting of the abrasive particles and therefore of the workpiece with a metal-dissolving, usually acid, liquid medium taking place in addition. Surfaces can be smoothed, flash removed, edges rounded, etc. by this method.
Known suppliers of this technology are the REM company and, particularly in the German area, the OSRO company. A special arrangement for the fine machining of blisks has become known from these suppliers. This uses an essentially rectangular, vibrating container with a trough-type volume open at the top for the abrasive filling. The container vibrations induced by an unbalanced rotor generate a quasi-continuous circulating motion of the abrasive filling, including a component of motion in the longitudinal direction of the xe2x80x9ctroughxe2x80x9d. The integrally bladed rotor disk, i.e. the blisk, to be machined is positioned with its centre line horizontal, transverse to the container longitudinal direction and freely rotatable at a defined height centrally over the container in such a way that it is immersed with its currently lower region within the container filling in the form of a segment, the immersion depth corresponding approximately to the radial blade height. Because of the longitudinal component of motion of the abrasive container filling mentioned, the rotor disk is put automatically into rotation in the manner of an xe2x80x9cundershoot mill wheelxe2x80x9d, i.e. a water wheel with its lower part immersed in a flow channel, so that with each revolution, its complete bladed periphery comes into contact with the abrasive filling. A disadvantageous feature of this arrangement is the unfavourable working time to xe2x80x9cidling timexe2x80x9d ratio for each blade because, due to the geometry, each blade moves only xe2x80x9cuselesslyxe2x80x9d through the air for the major part of a disk revolution. During this xe2x80x9cair phasexe2x80x9d only the adhering, metal-dissolving fluid acts, in a rather uncontrolled manner, on the surface. For this reason alone, a multitude of revolutions, i.e. a long processing period, is necessary before the desired surface quality is achieved. In addition, the kinematics of this xe2x80x9cmill wheel arrangementxe2x80x9d tend to generate relatively weak relative motions between workpiece and filling, which further lengthens the processing period. Whereas, in fact, the container itself vibrates/shakes relatively powerfully, the liquid-soaked abrasive particle filling moves, due to inertia, in the manner of a highly viscous fluid without effective vibration constituents, i.e. with a rather sluggish, directional flowing motion. Because the component/blisk is decoupled from the container and only turns slowly on its stationary holding device, there are only weak erosive relative motions overall. It should be mentioned, as an advantage of such an arrangement, that the container volume and therefore the filling volume can be minimised in relation to the component size.
On this basis, the object of the invention consists in providing an arrangement for liquid-supported vibratory grinding of rotationally symmetrical, disk-shaped or annular components, which arrangement permits much shorter throughput times for each component by optimising the erosion process and therefore operates more economically.
This object is achieved by means of the features characterized in claim 1, in association with the generic features in its preamble.
The essence of the invention is seen in the fact that the disk-shaped or annular component is arranged so that it is located horizontally in the container and is firmly/rigidly connected to the latter or, on the other hand, can be rotated about its centre line but is otherwise likewise firmly connected to the container, so that all the surfaces to be processed are continually in contact with the abrasive filling. The container shape is matched to the component and is therefore rotationally symmetrical, thus permitting a filling which covers the component. In consequence, there are no xe2x80x9cidling timesxe2x80x9d during the processing. Because of the stiff connection of the component to the container, the former executes the same vibration motions as the latter with, if appropriate, an additional rotary motion. The filling, which is sluggish due to its inertia, is in contrast more or less at restxe2x80x94apart from a slow, directional circulatory motionxe2x80x94so that the vibration amplitudes of container and workpiece/component are converted almost completely into abrasively effective relative motions. By this means, the desired material erosion is achieved in a substantially shorter time.
Preferred configurations of the arrangement according to the main claim are designated in the sub-claims.